Indigo

Indigo was obtained from Macklin (Shanghai, China), and oxindole was purchased from Energy Chemical Industries (Shanghai, China). Indole, isatin, and indigo derivatives were obtained from Aladdin (Shanghai, China). All chemicals purchased from commercial sources were used without further purification.

PAHs and heterocyclic compounds (PHE, NAP, ACE, FLN, ANT, FLU, BaA, PYE, CHR, DBT, DBF, CA, and indole) used for the degradation assay were purchased from Aladdin or J&K Scientific. Standards of metabolic intermediates, such as 1‐hydroxy‐2‐naphthoic acid, salicylic acid, 9‐fluorenol, 9‐fluorenone, indigo, and dibenzothiophene‐S‐oxide, were purchased from either Macklin or Sinopharm Chemical Reagent Co., Ltd. All water‐insoluble substrates were dissolved in N,N‐dimethylformamide (DMF) as stock solutions and the appropriate volume was added to the medium before use. BSTFA for derivatization of samples was purchased from Sigma‐Aldrich. The purity of all chemicals exceeded 99%. The PHE degraders were cultured with an MSM with PHE as the sole carbon source. MSM per liter consists of 3.7 g KH₂PO₄, 5.2 g K₂HPO₄·3H₂O, 2.0 g NH₄Cl, 1.0 g Na₂SO₄, 0.1 g MgSO₄, and 1 ml trace metal solution
⁴⁴ (link). Luria–Bertani (LB) broth medium (tryptone 1%, yeast extract 0.5%, and NaCl 1%) was used for the cultivation of E. coli and was supplemented with antibiotics when necessary. All abbreviations in the text are listed in Table S4.